Hydraulic installations with multiple pressures



P. E. MERCIER 3,204,573

HYDRAULIC INSTALLATIONS WITH MULTIPLE PRESSURES sept. 7, 1965 4 Sheets-Sheet 1 Filed Aug. 22, lees @wilg EN A m. wmf vm SCP- 7, 1965 P. E. MERCIER 3,204,573

HYDRAULIC INSTALLATIONS WITH MULTIPLE PRESSURES Filed Aug. 22, 1965 4 Sheets-Sheet 2 HYDRAULIC INSTALLATIONS WITH MULTIPLE PRESSURES Filed Aug. 22, 1963 P. E. MERCIER sept. 7, 1965 4 Sheets-Sheet 3 Sept' 7, 196-5 P. E. MERCIER 3,204,573

HYDRAULIC INSTALLATIONS WITH MULTIPLE PRESSURES United States Patent O '1 claims. (for. ras-22s) This invention relates to hydraulic installations with multiple pressures.

According to the invention there is provided a hydraulic installation comprising in combination at least two accumulators calibrated to clearly differing pressures, at least two utilization circuits of which one is branched Vbetween the two accumulators and at least one other is branched between the accumulator of highest pressure and a zone of lower pressure, a pump drawing a part of the time from the accumulator of lowest pressure and supplying the raccumulator of highest pressure, and means for completing the delivery of the pump, directed towards this accumulator of highest pressure, by a contribution formed from the zone ot lower pressure.

By virtue of such a combination of means, when certain utilization apparatuses ope-rate between two extreme pressures substantially remote from the highest pressure and the lowest pressure of the installation, it is possible to branch them between the two aforementioned accumulato-rs, instead of branching them between the high pressure accumulator and the reservoir, thus avoiding an expenditure of pressure at a high potential which is then permitted t-o deteriorate to the reservoir and the recharging ot the accumulators by a fresh pumping up to the calibration pressure, that is to say an unnecessary energy expenditure. Furthermore, since the pump sucks from an accumulator already under pressure, instead of from the reservoir, there is no fear of cavi'tation phenomena.

It is clear that the utilization of an accumulator at intermediate pressure lends itself to multiple uses, and that more particularly it is .possible to use it either yas receiver in relation to a utilization circuit interposed between the accumulator and the accumulator of relatively higher pressure, or as source of pressure uid for a utilization circuit interposed between it and the lower pressure zone. It on the average the operation as receiver' of the intermediate pressure accumulator is predominant, the installation possesses no partcula-r innovation; if on the contrary in the operation of the accumulator at least one circuit interposed between it land the lower pressure zone is predominant, the installation will utilize a distributor element of a type identical with that which was described in French Patent No. 1,344,926 entitled Hydraulic lnstallation Wit-h Multiple Pressures.

Finally it in succession and by periods of time the intermediate pressure accumulator operates as receiver and as source ot fluid under pressure, particular arrangements are provided in the present invention, which complete those of the preceding7 case above envisaged.

in one embodiment the pump, under the control of a iirst distributor, sucks from the lower pressure zone or from the accumulator of relatively lower pressure, according to whether the pressure in the latter is 'below or above a predetermined pressure, while a second distributor directs the oil delivered by the pump into the zone of lower pressure or into the relatively high pressure accumulator, according to whether the pressure in the latter is above or below a predetermined value, while in ail these cases means prevent the accumulatore from disddh/MHS charging through the circuit of the pump when it is not operating.

In one particular form of embodiment the pump is connected to the second distributor through a circuit which comprises element-s of the rst distributor adapted to isolate the second distributor and consequently the accumulator of lowest pressure from the pump, when the latter delivers into the Zone of lower pressure, that is to say when the accumulator at the highest pressure is charged, in order that the accumulator at the lowest pressure may not discharge into the Zone of lower pressure through the pump.

ln other embodiments the installation comprises a plurality of accumulators at relatively lower pressure, of which at least one of the two maximum and minimum utilization pressures is different, but t-he predominant operation of which is of the receiver type.

ln a modification comprising a plurality of accumulators at relatively high pressure, the means 4described and represent-ed in the aforementioned patent are further utilized, permitting on the one hand a delivery of liquid under pres-sure towards the accumulatore at relatively high pressures, from the single pressure source, when the pressure in at least one of thc accumulators drops below a predetermined value, and on the other hand the distribution of this delivery among the accumula-tors in accordance `with a predetermined law.

Finaily in another modification the accumulator at intermediate pressure operates between three pressures P1, P2, P2 staged in increasing ord-er. When the pressure of the intermediate pressure accumulator is lower than P2, it operates as source of iiuid under pressure between P1 and P2, land a selector element permits its recharging by the pump als source of pressure fluid concurrently with the high pressure accumulator; when the pressure of the accumulator is greater than P2, it operates as receiver and if its pressure is suiiciently close to P3 the pump sucks therefrom when it is under charge.

In this case the distributor element intervenes to recharge the intermediate pressure accumulator only if the pressure of the latter is between P1 and P2, while the tirst distributor, which permits sticking from the intermediate pressure accumulator when its pressure is between P2 and P3, isolates the intermediate pressure accumulator from the suction of the pump, which accumulator furthermore is preferably connected through a nonreturn valve to the delivery conduit which corresponds thereto on the distributor. llt tiren sulices that the second delivery conduit of the distributor, which corresponds to the relatively high pressure accumulator, is also provided with a non-return valve so that the distribution Y valve of the distributor can reconnect to the reservoir that of the two delivery pipes mentioned above which is not under charge, feeding directly from these two pipes the staged pistons of the circuit-closer so that the latter is subjected when the pump is under charge only to that of the pressures which corresponds to the accumulator which is being recharged.

The invention is illustrated by way of example in the accompanying drawings, in which:

FGURE l represents diagrammatically a hydraulic installation comprising an accumulator at a relatively high pressure and at least one accumulator at a lower pressure, branched in a particular fashion, recharging being effected by a single pump, the accumulator or accumulators at intermediate pressure operating in predominant manner as receivers;

FIGURE 2 represents a modification comprising two accumulators at lower pressures diiering from one another;

FIGURE 3 represents another modification comprising two accumulatore at relatively high pressures but different from one another, and a third accumulator of lower pressure operating essentially as receiver of uid issuing from at least one utilization circuit fed by one of the two accumulators of relatively high pressure, and

FIGURE 4 is similar to FIGURE 3, in its general principle, but comprises only one accumulator at relatively high pressure and one accumulator at intermediate pressure functioning between three pressures P1, P2, P3.

The installation of hydraulic accumulators as represented in FIGURE l comprises a high pressure accumulator 1 and an intermediate pressure accumulator 2, calibrated at pressures for example 120 kg./sq. crn. and 80 lig/sq. cm. approximately. The major part of the utilization circuits -designated as a whole by 3 is intended to be branched between the high pressure accumulator 1 and the intermediate pressure accumulator 2. However the installation can also comprise as accessories utilization apparatuses 3a, 3b, branched between these accumulators and a Zone 6 `of lower pressure called the reservoir, through the intermediary of appropriate pipes terminating on the one hand at the accumulators 1 or 2 and on the Iother hand at the reservoir (tube 32 bias).

Through the intermediary of apparatuses which will be described, a pump 4 delivers the liquid, in the present case oil, always into the high pressure accumulator 1, while it sucks from the intermediate pressure accumulator 2, as long as the pressure in the latter is above a predetermined lower limit, whereafter if necessary, that is to say if the pressure in the high pressure accumulator 1 is not yet suiicient, the pump continues to suck but from the reservoir designated by 6.

A low pressure may prevail incidentally in the reservoir 6, especially if the installation comprises a charging pump delivering into the said reservoir.

The apparatuses in question are constituted by two hydraulic distributors 11, 12 which hereinafter will be called reverser and make-and-break respectively. The reverser serves for permitting the pump 4 to suck either from the intermediate pressure accumulator 2 or from the reservoir d.

This reverser distributor is constituted by a slide valve 13 which can slide in a cylinder 14 tixed in a body 15 constituted, for reasons of manufacture and assembly, of three parts 15a, 15b and 15C. One of the ends of the slide valve 13 is subjected, through a conduit 16 and a pipe 17, to the pressure prevailing in the intermediate pressure accumulator 2, while its other end is pushed in the opposite direction by a return spring constituted in this example by a square torsion bar in extension of a spindle 18, one end of which is tted into the body 15, while its other end is iiXed to the spindle 18 per se fast with a cam lever 22 which presses against the roller 21 carried by the corresponding end of the slide valve. In order to ensure stability of function of this distributor, that is to say a very free movement in both directions, the assembly is designed in such fashion that as the slide valve 13 through its roller 21 pushes back the cam level 22, the elastic force opposing the movement of the slide valve 13 decreases despite the increase of the resistance due to the spring of square section extending the spindle 18.

When the slide valve 13 yoccupies its extreme left position, it cuts oii" communication between the two conduits 16 and 24 and at the same time it places the latter in communication with chamber 25 of the body through the intermediary of an annular groove 26, a radial channel 27, a longitudinal channel 23 and another radial channel 29 of t-he slide valve.

The chamber 25 of the body 15 is permanently connected to the reservoir 6 through a conduit 31 of the body `and a pipe 32.

The make-and-break 12 has a double function in that it serves firstly as reverser in order to connect the delivery conduit 34 of the pump with either the conduit 35 for recharging the high pressure accumulator 1, when the pressure in the latter is insuiiicient, or with the reservoir in the contrary case, and furthermore it permits isolating the intermediate pressure accumulator 2 from the reservoir, while the pump delivers into the reservoir when the high pressure accumulator 1 is under a sufcient pressure so that, during this time, the intermediate pressure accumulator does not discharge into the reservoir, as will be explained hereinafter.

The malte-and-break 12 comprises a cylindrical slide valve 37 mounted for sliding movement in a cylinder 33 iixed in a body designated generally 39 and constituted, for reasons of manufacture and assembly, of tour parts 39a, 3%, 39C and 39d suitably assembled.

@ne of the ends of the slide valve 37 is subjected to the pressure of the high pressure accumulator 1 through the intermediary of a conduit 41 and the pipe The other end of the slide valve is subjected to the action of a return spring 42 through the intermediary of a cam lever 43 and a roiler 44 carried by the slide valve 37 in an arrangement similar to that described above for the reverser distributor 11, the cam lever 43 coming to bear, at the end of the stroke, against an elastic stop 45.

A conduit 47 of the make-and-break is connected through a pipe 48 to the conduit 24 of the reverser 11, and another conduit 51 of the make-and-break can be placed in communication according to choice either with the conduit 47, through a wide annular groove 52 of the slide valve 37, or with chamber 53 of the body 39 through an annular groove 54, a radial channel 55, a longitudinal channel 56 and a radial channel 57 of the slide valve. The conduit 51 is permanently connected to the suction tube of the pump 4 through a pipe 58 and also the chamber 53 is permanently in communication with the reservoir 6 through a conduit 59 and a pipe 61,

The circuit which permits the connecting of the pump 4 to the reservoir comprises the pipe 34, a conduit 63 of the body of the make-and-break, then in the slide valve 37, an annular groove 64, a radial channel 65, the longitudinal channel 56, the radial channel 57 and nally the chamber 53, the conduit 59 and the conduit 61.

The circuit which permits placing the pump 4 in communication with the high pressure accumulator 1, in order to recharge it, comprises the pipe 34, the conduit 53, a wide annular groove 66 of the slide valve, a conduit 67 and the pipe 35.

The positions of the various elements represented in the drawing signify that the pressure prevailing in the high pressure accumulator 1 is suicient so that the latter has no need of being recharged for the moment. In fact the pressure prevailing in this accumulator is transmitted, through the pipe 35 and the conduit 41, to the corresponding end of the slide valve 37, against its return spring 42 fast with the spindle and the cam lever, so that the delivery of the pump is connected to the reservoir by the following path: pipe 34, conduit 63, annular groove 64, radial channel d5, axial channel 56, radial channel 57, chamber 53, conduit 59 and pipe 61.

1f the pressure in the high pressure accumulator 1 drops below its minimum acceptable value, it is no longer suthcient to push back the slide valve 37 of the makeand-break against its return spring 42. The slide valve thus moves towards the left in relation to its position as represented in the drawing, so that the pump then delivers oil into the accumulator 1 by the `following path: pipe 34, conduit 63, annular groove 66, conduit 67 and pipe 35. The oil is sucked by the pump either from the intermediate pressure accumulator 2, if the pressure prevailing therein is sutlicient, or from the reservoir. The suction from the intermediate pressure accumulator 2 takes place by the following path: pipe 58, conduit 51, annular groove 52, conduit 47, pipe 43, conduit 24, cylinder 14, conduit 1d and pipe 17. llf the pressure in the intermediate pressure accumulator 2 is insuiiicient, the slide valve 13 closes the conduit 2liand consequently isolates the accumulator, while the suction of the pump then takes place from the reservoir by the following path: pipe 5?, conduit 5l, annular groove 52, conduit d?, pipe d3, conduit 2d, annular groove 26, radial channel 2'7, longitudinal channel ZS, radial channel 29, chamber 25, conduit 31, pipe 32 and reservoir 6.

Furthermore, the circuit of the intermediate pressure accumulator 2 is isolated from the reservoir irrespective of the pressure prevailing in the said accumulator. in fact if this pressure is relatively high, as represented in the drawing, that is to say sufficient to push back the slide valve i3 of the reverser il, the accumulator 2 is in fact in communication with the conduit 2d of the distributor, but the latter is in communication only with the pipe dit, the conduit 4'7 and the annular groove 523 of the slide valve 37 of the make-and-break. Here two cases can arise: In the iirst case, the accumulator l is charged (position represented in the drawing) and the groove Si?. is closed, and in the second case, if the accumulator 1 is discharged, it is in the course of recharging, so that the groove 52 is then connected to the suction side of the pump which, at this moment, no longer delivers into the reservoir but into the high pressure accumulator l.

Ii the pressure prevailing in the accumulator 2 is relatively low, it is not sufficient to force back the slide valve 13 and then it is apparent that the accumulator is no longer connected to the conduit 24 and cannot be in communication with the reservoir.

ln summary, the pump delivers always into the high pressure accumulator l, it recharges the latter each time there is need, sucking oil either from the intermediate pressure accumulator 2, if the pressure in the latter is suliicient, or from the reservoir if the said pressure is insuilicient.

By sucking oil from an intermediate pressure accumulator instead of sucking it from the reservoir, one avoids `the phenomena of cavitation at the suction of the pump.

In a irst modication, represented in the FIGURE l, the installation comprises in addition to the apparatuses already described and represented in solid lines in this figure, other apparatuses represented in broken lines.

These supplementary apparatuses consist of a plurality (two in the example) o intermediate pressure accumulators 2a, 2b, calibrated at the same minimum pressure as the intermediate pressure accumulator 2, but intended to supply utilization circuits 7l, 72 capable of functioning up to pressures which have risen to values diierent from one another and from the maximum pressure at which the utilization apparatuses 3b fed by the accumulator 2 can still work.

The supplementary intermediate accumulator 2a is supplied from the high pressure accumulator il through the intermediary of a utilization circuit 36 branched between these two accumulators.

In asimilar manner the supplementary intermedi-ate pressure accumulator 2b is intended to be supplied also from the high pressure accumulator l through the intermediary .of a utilization apparatus 3d.

1n order thatthe intermediate accumulators 2a and 2b are not in danger of delivering one into the other they are provided with non-return valves '73, '74, 7S respectively. On the other hand the accumulator 2, as in the case where it is employed alone, comprises no non-return valve. This cannot be otherwise since, when the piston 13 of the distributor dit returns tothe left and has masked in its rst displacement the orifice bored in the cylinder 14 opposite the pipe 24, it could not complete its movement if liquid did not ilow back towards the accumulator 2.

The use :of a plurality of intermediate accumulators such as 2a, 2b, etc., is especially indicated in the case where the arrangement serves operational cycles, each of the accumulators being for example allocated to a partial operation, and all these accumulators a-t the commence rment of each cycle being at one and the same minimum pressure .defined .by the elastic device of the reverser lll, while when they have fulfilled their task the accumulatore can possess variously staged pressures above this minimum pressure.

Such a staging of the pressures of the intermediate pressure `accumulatore at the end of the operations to which they are allocated, for each cycle, can be mod-ied by the adjustment of the capacities of the accumu-la'tors with the aim of facilitating the regulation and eXibil-ity of running of the servo-arrangement considered as a whole.

Obviously such arrangements lare of more general use than that which `is given only by way of example.

When the high pressure accumulator l needs to be r-echarged, the slide valve of the make-and-break 12 shifts towards the lett, `as explained above, and the pump delivers oil into the accumulator. The pressure of that of the three intermediate accumulatore 2, 2a, 2b which is greater than that of the two others `is transmitted, through the pipe i7 .and the conduit 16, to the piston 13 of the reverser distributor fit1. lf this pressure is suticient, the slide valve i3 is pushed back thereby and the pump consequently sucks from the intermediate accumulator in question.

On the other hand if this pressure is insuilicient the slide valve .i3 is not pushed back and the pump then sucks yfrom the reservoir i6, through the lintermediary of the internal channels of the slide valve ,'13 and `of the chamber 25 of fthe reverser distributor 1l.

llt is `quite apparent that the pressure of that of the intermediate accumulators which is highest keeps the two non-return valves of the other two accumulatore closed. When the pump sucks from an intermediate accumulator, thus it sucks lfrom that which is still at the highest pressure. The intermediate accumulators recharge themselves only from the high pressure accumulator il, which is itself recharged by the pump.

In FIGURE 2 there is represented a modification of the installation according to lFIGURE, 1, with one single accumulator .l at relatively high pressure Iand two .accumulators 2 and 2c calibrated at lower pressures differing from one another, the pressure of the accumulator 12e ybeing lower than that of the :accumulator 2. There are always utilization apparat-uses 3a between the Aaccumulator l at highest ypressures and the reservoir, utilization apparatuses 3b between the lower pressure acciunulator 2 and the reservo-ir, utilization apparatuses 3i lbetween the accumulator d and the accumulator 2 and yfurthermore there are utilization apparatuses 3e between the .accumulator 1 and the accumulator 2c, and also utilization ap para'tuses :if between the accumulator :2c and the reservoir.

In comparison with the embodiment according tto `FIG- URE l there is no change as regards the accumulator 'l at relatively high pressure, the lower pressure accumulator 2 and the make-andbreak i12 which permits the charging of the accumulator ll from the pump al, On the other hand the distributor lila has a solid slide valve and serves now -only to interrupt or permit connection between the conduits lo and 2d. There is simply added a reverser' distributor ylll associated with the supplementary accumulator 2c exactly in ythe same manner as the reverser distributor lll was 4associated with 'the accumulator 2 in FIGURE l. However in order to avoid any one of the two accumulators `2 yand 2c 'being able tto discharge into the other, on the conduits 48 and 48a issuing from the -two `distributors 1l and 'Illa there have been disposed non-return `valves 78 and '78a respectively.

The remainder of lthe installation, for which the same reference numerals have been retained for the designation of Kthe same elements, will not -be described.

The operation of this installation is entirely similar to i that according to FIGURE 1: When fthe accumulator 1 is charged, the make-and-break 39 causes the pump 4 to deliver in closed circuit into the reservoir. On the :other hand when the accumulator `1 is discharged below a predetermined pressure, the make-and-break causes the pump to deliver into the accumulator, through the conduit 35.

-If the lower pressure accumulators 2 and 2c are suticiently charged, the corresponding ldistributors .11a and 111 permit the pump to suck from the accumulators and the suction incidentally will take place `from that Iwhich is at the higher pressure. lf the pressure in the accumulator 2 is not suflicient, the suction of the pump takes place through the intermediary of the reverser :distributor 11, either from the accumulator 2c if its pressure is suicient, or `from the reservoir if the pressure of the accumulator 2c is insufficient.

In more general fashion, for any number of :accumulators :similar -to the two accumulators 2 and 2c, only the distributor connected to the last accumulator, calibrated to the lowest pressure (namely the distributor 11 in the example as described) is a reverser distributor, while the others, similar to the distributor 11a, serve only to permit yor interrupt the passage of the liquid between lthe corresponding accumulator and the pump.

In FIGURE 3 another modification is shown, wherein the installation comprises two accumulators and la at relatively high pressures differing from one another, and an intermediate pressure accumulator 2, the principal utilization apparatuses, such as 3 and 3h, being branched between each of the two relatively high pressure accumulators 1 and 1a and the intermediate pressure accumulator 2 respectively.

Between each of the three accumulators and ythe reservoir 6 there are utilization apparatuses 3a, 3g and 3b respectively.

In this installation the intermediate pressure accumulator 2 is recharged from the two higher pressure accumulators 1, la, through the two corresponding utilization circuits 3 and 3h. The two relatively high pressure acicumulators 1 and 1a are recharged from the pump 4, under the control of a device of the nature of that described in the aforementioned French patent.

As in the embodiment accord-ing to FIGURE l, the pump 4 sucks from the intermediate pressure accumulator 2 under the control more especially of the reverser distributor 11, in such manner that when the p-ressure in the intermediate accumulator 2 drops below a predetermined lower value, the pump 4 instead of sucking from the accumulator 'sucks then from the reservoir, as described above.

Furthermore the pump y4 delivers oil under pre-ssure into one or the other of the two relatively high pressure accumulators 1 and la, when the pressures therein become insufficient, this taking place under the control of two hydraulic distributors designated `generally respectively 91 and 92, the hydraulic distributor 91 already comprisingr all the elements of the distributor 12 according to FIG- URE l (for which the same reference numerals have been retained) and vfurthermore supplementary elements which permit it to be sensitive to the two pressures prevailing in the two accumulators 1 and 1a respectively.

These elements comprise a conduit 94 of the body of the distributor 91, which has the same task as the conduit 41 in FIGURE 1, but which for reasons of manufacture and assembly acts upon an extension 95' of the slide valve 37 `of the distributor, the extension being constituted by an independent piston which slides in a cylinder 96 tast with the body of the distributor, the piston 95 pressing upon the corresponding end of the slide valve 37. The conduit `94 is permanently connecte-d through a pipe 99 with the high pressure accumulator 1.

The body of the distributor 91, which again plays the part of a make-and-break, comprises another conduit 1411 permanently connected `to the other relatively high pressure accumulator 1a, and which is intended to subject annular face 1113, constituted by the part not covered by the piston 95, of the end of the slide valve 37 to the pressure cf this accumulator.

The distributor 92 is of the type `as described and represented in detail in the aforementioned French patent. It comprises essentially a reverser distributor constituted by a -sleeve `107 mounted yfor sliding7 on a iixed hub 108 and operated through the intermediary of a rocker lever 1159 by two pis-tons 111, 112, subjected permanently to the pressures `of the accumulators 1 and 1a respectively.

The details of the structure and :operation of the distributor 92 have been set forth in detail in the aforementioned patent, to which one can refer. It will be recalled simply that the arrival of Ioil under pressure takes place in conduit 113 and that under the control .of the sliding sleeve 1157 it is directed either into cond-uit 114 connected to the laccumulator 1 or into conduit 115 connected tothe accumulator 1a.

A chamber 129 and the radial passages terminating at the conduits y114i and 11S are established in such manner that in the middle position of the sleeve 1117 the distributor Oilers to the pump a sufficient delivery section, a nonreturn valve possibly being disposed in the immediate vicinity of the conduits 114 and 115.

The operation ofthe installation is as follows:

The slide valve 37 of the make-and-break 91 is permaneatly subjected to the total of the pressures prevailing in the accumulators 1 and 1a and to the action of its return spring `42. When the pressure in at least .one of the two accumulators 1, 1a drops below a predetermined value, the slide valve 37 of the ymake-and-break is pushed back by its return spring, so that the pump then delivers through the conduit 110 into the conduit 113 of the distributor 92. The latter directs the oil under pressure in-to that of the two accumulators 1 or A1a which is the more discharged.

As regards the suction of the pump, this takes place through the intermediary of the reverser distributor 11, either into the intermediate pressure accumulator 2, if the pressure prevailing therein is above a predetermined value, or into the reservoir 6 if on the contrary the accumulator 2 is discharged below this lower limit.

In FIGURE 4 there is represented the modication according to which there are available a relatively high pressure accumula-tor 1 and an intermediate pressure accumulator 2, principal utilization apparatuses such as 3, 3a, 3b, interposed respectively between the accumulator 1 and the accumulator 2, between the `accumulator 1 and the reservoir 6, and between the accumulator 2 and the reservoir 6. According to the relative deliveries of the utilization apparatuses 3 and 3b, the accumulator 2 acts as receiver or as source of pressure fluid. Thus it will operate between three pressures P1, P2, P3, enumerated in the yorder of increasing pressures and designating its actual pressure by P1, if P1 P2, it will have to be recharged by the pump 4, while if P1 P2, it will furnish liquid to the pump 4 whic-h will deliver it into P1 if the pressure of P1 is less than a specific pressure.

The ele-ments represented in FIGURE 4 are identical with those according to FIGURE 3 as regards the makeand-break k91 and the element 11. The distributor 92 is also similar to that according to FlGURE 3 with the eX- ception of the sleeve 197 sliding on the xed hub 108, the length of which is reduced so as to uncover that of the radial conduits which is not in communication with the central annular cavity 124i of the sleeve 197 and the two conduits in question simultaneously in the middle position of the sleeve 107.

In these circumstances that of the conduits 114 or 115 which is not under charge is in communication with the reservoir through the conduit 121 and the conduit 122 (in the case of the iigure it is the conduit 115 which is connected to the reservoir). The lay-out of the conduits between the two accumulators 1 and 2 and the three elements, the distributor 92, the reverser 11 and the makeand-break 91, is as follows: The accumulators 1 and 2 are connected respectively, without interposition of non-return valves but with interposition of delay constrictions 104', 105', to the conduit 116 and 117 of the element 92 and to the entry orifices of the principal utilization apparatuses 3 and 3a for the accumulator 1, 3b for the accumulator 2. The exit orifices of the principal utilization apparatuses are connected respectively to the accumulator 2 for the utilization apparatus 3 and to the reservoir for the other two apparatuses. The conduits 114 and 115 of the distributor 92 are connected directly to the conduits 94 and 101 of the make-and-break without interposition of a constriction, and through the intermediary of the non-return valves 118 and 119 to the accumulators 1 and 2. All the other connections as in FIGURES 3 and 4 are unchanged.

The operation is easy to understand. If the pressure in the accumulator 2 is equal to its maximum value (the case in the ligure), the piston 13 of the reverser is pushed fully to the right. The distributor is in the position of charge towards the accumulator 1, the pressure of the accumulator P2 being maximum and pushing the piston 112 of the distributor 92. The charging of the accumulator 1 being completed, the make-and-break isolates the pump, its piston occupying its extreme right-hand position and the pump communicates with the reservoir on the delivery side through the conduit 63, the radial conduit 65, the axial channel of the slide valve 37, the radial channel 57, the chamber 53, the conduit 59 and the conduit 61, while it also sucks from the axial channel of the slide valve 37 through the conduit 51.

If the pressure in the accumulator 2 now drops below its intermediate valve 132 the piston 13 of the reverser 11 recoils towards the left and isolates the conduit 1'7.

It will be observed that in all the cases where the pump is charging, the make-and-break is subjected only to the action of the pressure prevailing in that of the accumulators towards which the distributor directs the charge (the accumulator 1 in the case of the figure). if the pressure in the accumulator 1 is suti'icient, the distributor tilts the conduit 113 which receives the liquid delivered by the pump when it is charging, is placed in communication with the conduit 115 by the displacement downwards of the sleeve 107 driven by the rocking of the lever 109 of the distributor 92. During the rocking of the lever 109, which is retarded by the constriuctions 104, 105, and by reason of the simultaneous uncovering of the two radial conduits of the hub 108, which control the conduits 114, 115 of the distributor, in the course of the rocking of the said lever 109 the conduits 94 and 101 of the make-andbreak are temporarily and simultaneously connected to the reservoir, permitting the staged piston 37 of the makeand-break to return to the left under the action of the spring pushing the cam lever 43. 1n its new position the distributor valve of the distributor 92 thus directs upon the conduit 101 of the make-and-break a pressure equal to that prevailing in the accumulator 2 which is set to charge immediately and remains thus during an interval of time which depends upon the shape of the lever 109, the characteristics of the accumulatore 1 and 2, of the utilization apparatuses, etc.

lf the relative pressure ratios of the two accumulators are sutiiciently modified before the accumulator 2 has reached its mean pressure P2, the distributor will recharge the accumulator 1 before completing the charging of the accumulator 2 in accordance with a procedure similar to that which has just been described.

The invention is not of course limited to the forms of embodiment as described and represented. For example the installations could be equipped with a number of accumulators differing from those adopted in the installations as described.

I claim:

1. A hydraulic fluid pumping and storage plant for producing hydraulic forces comprising, in combination, a high pressure accumulator, at least one accumulator calibrated to a pressure lower than that of said high pressure accumulator, a liquid storage reservoir, a continuously operating pump having an inlet and outlet, said pump being adapted to supply liquid from said reservoir to each of said accumulators, a first valve having a rst port communicating with said low pressure accumulator, a second port communicating with said reservoir, and a third port of the iirst valve, and second resilient means in in one position to connect said third port with said iirst port and in another position to connect said third port with said second port, first resilient means in said valve to urge said member towards said another position thereof, said member being movable towards said one position thereof against the action of said resilient means in response to liquid pressure stored in said low pressure accumulator, a second valve connected with said high pressure accumulator, with the pump inlet, the pump outlet, said reservoir and with said third port of the iirst valve, a movable valve member for said second valve effective in one position to connect said pump outlet with said pump inlet and with said reservoir, and eiective in another position to connect said pump outlet with said high pressure accumulator and said pump inlet with said third port of the iirst valve, and second resilient means in said second valve to urge said member of the second valve towards said another position thereof, said valve member of the econd valve being movable towards said one position thereof against the action of said second resilient means in response to liquid pressure stored in said high pressure accumulator whereby said pump will stick liquid from said reservoir through said rst valve and said second valve when the liquid pressure in said high pressure accumulator and in said low pressure accumulator is below a value determined by said first resilient means and by said second resilient means, but will suck pressure liquid from said low pressure accumulator through said lirst and second valves when the liquid pressure in said high pressure accumulator is below said value and the liquid pressure in said low pressure accumulator above said value, or said pump will suck liquid from the pump outlet through said second valve when the liquid pressure in said high pressure accumulator is above said value, and this irrespective of any pressure variation in said low pressure accumulator.

2. The plant as claimed in claim 1, further comprising means to prevent discharge of the accumulators to the pump when the latter is not operating.

3. The plant as claimed in claim 1, wherein said tirst resilient means and said second resilient means are so designed that the eiiort exerted by the saine upon the correspondi-ng movable valve member decreases as the latter are displaced in response to the liquid pressure stored in said accumulators, but increases when said valve members are moved under the action of said resilient means.

1i. The plant as claimed in claim 3, wherein said rst and second resilient mea-ns comprise each a pivotable lever having a cam-shaped end in Contact with the corresponding movable valve member.

5. The plant as claimed in claim 1, comprising a plurality of low pressure accumulators calibrated to substantiaily the same pressure, each low pressure accumulator being connected to said iirst valve through a check valve preventing the iiow of pressure liquid from the first valve to the low pressure accumulator, and a utilization device interconnected between said high pressure accumulator and each of said low pressure accumulators as well as between each of said low pressure accumulators and said reservoir.

6. The plant as claimed in claim 1, comprising two low pressure accumulator-s calibrated to diierent pressures, the accumulator calibrated to a pressure intermediate that of the other low pressure accumulator and that of said high pressure accumulator being connected to said pump through a valve adapted to interrupt said l ll Z connection when the pressure of the intermediate pressure Reerences Cited by the Examiner accumulator decreases below' a predetermined value. UNITED STATES PATENTS '7. The plant as claimed 1n clalm l, compnsmg two 10W pressure accumulators calibrated to different pres- 2,279057 4/42 Reed- 60-52 sures, means for causing delivery of pressure liquid from 5 212901479 7/42 Mermet 60-51 2,802,336 8/57 Ball 60-51 said pump to said two low pressure accumulators when the pressure in at least one of the two low pressure ac- FOREIGN PATFNTS cumulators decreases below a predetermined Value7 and A ,A

a distributor valve adapted to distribute said delivery of 540,183 10/41 Great Bummpressure liquid to said two low pressure accumulators and 10 Y y u A A I to said high pressure accumulator in accordance with a LAURENCE V E* NER P'lmmy Examine" predetermined law. ROBERT M. WALKER, Exmm'ner. 

1. A HYDRAULIC FLUID PUMPING AND STORAGE PLANT FOR PRODUCING HYDRAULIC FORCES COMPRISING, IN COMBINATION, A HIGH PRESSURE ACCUMULATOR, AT LEAST ONE ACCUMULATOR CALIBRATED TO A PRESSURE LOWER THAN THAT OF SAID HIGH PRESSURE ACCUMULATOR, A LIQUID STORAGE RESERVOIR, A CONTINUOUSLY OPERATING PUMP HAVING AN INLET AND OUTLET, SAID PUMP BEING ADAPTED TO SUPPLY LIQUID FROM SAID RESERVOIR TO EACH OF SAID ACCUMULATORS, A FIRST VALVE HAVING A FIRST PORT COMMUNICATING WITH SAID LOW PRESSURE ACCUMULATOR A SECOND PORT COMMUNICATING WITH SAID RESERVOIR, AND A THIRD PORT OF THE FIRST VALVE, AND SECOND RESILIENT MEANS IN IN ONE POSITION TO CONNECT SAID THIRD PORT WITH SAID FIRST PORT AND IN ANOTHER POSITION TO CONNECT SAID THIRD PORT WITH SAID SECOND PORT, FIRST RESILIENT MEANS IN SAID VALVE TO URGE SAID MEMBER TOWARDS SAID ANOTHER POSITION THEREOF, SAID MEMBER BEING MOVABLE TOWARDS SAID ONE POSITION THEREOF AGAINST THE ACTION OF SAID RESILIENT MEANS IN RESPONSE TO LIQUID PRESSURE STORED IN SAID LOW PRESSURE ACCUMULATOR, A SECOND VALVE CONNECTED WITH SAID HIGH PRESSURE ACCUMULATOR, WITH THE PUMP INLET, THE PUMP OUTLET, SAID RESERVOIR AND WITH SAID THIRD PORT OF THE FIRST VALVE, A MOVABLE VALVE MEMBER FOR SAID SECOND VALVE EFFECTIVE IN ONE POSITION TO CONNECT SAID PUMP OUTLET WITH SAID PUMP INLET AND WITH SAID RESERVOIR, AND EFFECTIVE IN ANOTHER POSITION TO CONNECT SAID PUMP OUTLET WITH SAID 